By using first principles calculations, we propose a codoping method of using acceptors and donors simultaneously to realize low-resistivity and high carrier concentration p-type ZnS with wurtzite structure. The ionization energy of single can be lowered by introducing the (III = Al, Ga, In) passivation system. Codoping method in ZnS (2N, III) has lower formation energy comparing with single doping of N since III elements act as reactive codopants. 1. Introduction Wide bandgap semiconductors, such as ZnX (X = O, S, Se), have attracted attention due to their potential application in short-wavelength light-emitting devices. Unfortunately, the doping unipolarity, that is, it can be doped either p-type or n-type, but not both, impedes the implementation of the materials [1]. Earlier researches show that ZnS and ZnO are difficult to be doped as p-type due to asymmetric doping limitation [1–3]. In order to obtain low-resistivity p-type ZnS, single doping and codoping methods are studied. Nakamura et al. fabricate Li-doped ZnS by a low-pressure metal organic chemical vapor deposition technique [2]. They find that it is p-type conductivity, and the acceptor ionization energy is about 196？meV, which is larger than the calculated results of 155？meV by Gai et al. [3]. Gai et al. calculated ionization energies for possible single doping method to obtain p-type ZnS [3]. The result shows that N-doped ZnS is promised to be p-type, but the ionization energy is calculated to be 144？meV, which is still deep acceptor level. In recent years, codoping method was suggested to solve the unipolarity of semiconductor [1, 4, 5]. P-type doping in ZnO is realized by codoping with N acceptors and Ga donors in the ratio of N？:？Ga = 2？:？1 [6, 7]. For p-type ZnS, experimental researches realize it by codoping with N and Li dual acceptors, and the hole concentration is measured to be 1018？cm？3 [8]. Theoretical investigations show that the codoping method of acceptor-donor-acceptor is more efficient than the single-doping method. They realize p-type ZnS by codoping with N acceptors and In or Al donors based on first principles calculations [9–11]. Codoping method makes the acceptor levels broaden and delocalize compared with the single doping of N. In addition, p-type ZnS nanocrystals can be obtained by codoping with N and Ga, In, or Al [12]. However, earlier researches about p-type ZnS with codoping method mainly focus on the density of state analysis. Quantifiable parameters, such as acceptor ionization energy and formation energy, are not presented. In addition, they have studied the
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